Enzymes are proteins synthesized by living organisms which can catalyze specific biochemical reactions such as the conversion of starch to sugar (amylase), the hydrolysis of fats to glycerol and fatty acids (lypase) and the hydrolytic breakdown of proteins (protease). It is commonly believed that enzymes are capable of catalyzing reactions only at a limited number of specific sites commonly referred to as "active sites".
Certain biological materials such as proteins, lipids and polysaccharides can be difficult to remove from substrates such as dishes, flatware and fabrics as such biological materials are substantially insoluble in traditional cleaning media. To increase the solubility and thereby effect removal of such biological materials, it is known to employ an enzyme in a cleaning media to catalytically assist in breaking down such materials into insoluble monomeric and/or oligomeric molecules. Certain types of enzymes such as amylase, lipase, and protease are known to be particularly useful for such purposes as they can effectively remove such materials from substrates without significantly degrading the substrate being cleaned.
Halogen bleaches are a well known group of chemical compounds having the ability to remove stains such as those caused by coffee and tea from a substrate. Halogen bleaches eliminate such stains by breaking down the large colored organic molecules which form such stains into smaller colorless molecules.
The cleaning actions of enzymes and halogen bleaches are complementary, each affecting different aspects of the soils typically found on dishes, flatware, and fabrics. Accordingly, a superior cleaning composition could be formed by employing both an enzyme and a halogen bleach in a single cleaning composition. However, while simple in theory such a combination has proven to be difficult to implement as halogen bleaches tend to instantly deactivate enzymes at concentrations as low as 1 part active halogen per one million parts cleaning media. While such deactivation of enzymes is not fully understood, it is believed that the halogen bleach affects either a change in the structure of the enzyme's active site or a change in the shape of the enzyme such that the enzyme's active site is no longer available as a reactor site.
Early attempts to combine a halogen bleach and an enzyme into a stable cleaning composition included the incorporation of a stabilizing amount of a polysaccharide into the cleaning composition, the incorporation of a stabilizing amount of a nonionic polymer into the cleaning composition, and coupling of the enzyme to an insoluble support. All of these early attempts met with limited success, encouraging research into other methods.
A slightly more successful attempt at combining a halogen bleach and an enzyme into a stable cleaning composition comprised encapsulation of the bleach in a time release coating. The time release coating delayed the release of the enzyme deactivating bleach for a time period sufficient to allow the enzyme to perform its cleaning function before it was deactivated. Unfortunately, this attempt also met with limited success as it proved virtually impossible to economically prevent premature release of an enzyme deactivating amount of the bleach.
A still slightly more successful attempt at combining a halogen bleach and an enzyme into a stable cleaning composition is disclosed in U.S. Pat. No. 4,421,664, which teaches that enzyme activity may be maintained in the presence of a halogen bleach by encapsulating the bleach in a time release coating and incorporating an amount of a reducing agent into the composition sufficient to substantially instantaneously reduce all prematurely released bleach. While this method has proven much more successful than earlier attempts, it has been discovered that in order for this method to work effectively it is necessary to employ an encapsulated bleach having an extremely high encapsulation efficiency which results in a prohibitively expensive composition.
Accordingly, a substantial need exists for an inexpensive and stable cleaning composition containing both an enzyme and a bleach wherein both the enzyme and the bleach may perform their desired cleaning function.